A lovely set of numbers - now to clean up at poker

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A French computer science student has stunned the world of
mathematics by working out the 13th root of a 200-digit number in
his head in under nine minutes.

By arriving at the 16-digit answer from 390 trillion
possibilities, Alexis Lemaire, 24, pulled off the most difficult
feat of mental arithmetic that has ever been attempted.

Thirteenth roots are a yardstick in mental arithmetic, because
13 is a prime number whose roots cannot be obtained by combining
those of other numbers.

Yet Mr Lemaire appeared only mildly satisfied by his feat. At
his next record attempt, he said, his brain would work even
faster.

"As this was my first attempt, I was cautious."

On June 3, he will try to find the right answer in less than
three minutes. In a few months, he believes that he will break the
one-minute barrier. "If I do that, without being pretentious, it
will probably be the best piece of mental calculation ever," he
said.

Mr Lemaire has spent four years developing a secret matrix
technique in which he memorises thousands of inter-linked tables of
numbers to aid his calculations. "It's just like learning your
times tables really," he said. "But the numbers are bigger."

Mr Lemaire now wants to find practical uses for his skill:
learning 40 languages simultaneously or becoming a "card sharp" to
clean up at poker.

"It's all about thinking visually," he said. "I have a map or
matrix in my head of thousands of tables that I have learned side
by side. I can scroll through them and pick out the numbers I
need."

For anyone seeking to challenge his record, Mr Lemaire has an
invaluable tip: all answers begin with the number 2.